This proposal seeks continuation funding to develop and support a vast archive of large-scale microdata drawn from 163 censuses of 43 European and Asian countries enumerated over the past half century. These data are a vital component of the Integrated Public Use Microdata Series (IPUMS), one of the most intensively-used resources for population and health research. The improved and expanded database will allow investigators to make comparisons across dozens of countries during decades of transformative change and will result in substantial new health-related analyses of the interrelationships of economic development, fertility and mortality decline, international migration, and family change. The Eurasian microdata archive represents a permanent and substantial contribution to the world's population research infrastructure. By making these data easily accessible to researchers and developing comprehensive and comprehensible documentation, the project is stimulating new scientific studies that transcends national boundaries and static interpretation. The project has four major goals: (1) Expand the database, adding data for six new countries and new 2010 round samples for countries currently in the database. (2) Enhance data and metadata, including new geographic coding to better support consistent cross-national and cross-temporal analysis, a new internationally-comparable living standards index based on housing characteristics, and a new socioeconomic indicator based on occupation and educational attainment. (3) Improve data infrastructure and access by implementing an Application Programming Interface, innovative new data structures, and a virtual data enclave. (4) Ensure dissemination and sustainability through user support, training and outreach, and implementation of a new plan to ensure long-run preservation of the data and metadata. This infrastructure is a basic resource for health research and policy analysis. Models and descriptions of the past underlie both theories of past social change and projections into the future. Accordingly, the data series provides a unique laboratory for the study of health and demographic processes and provides the empirical foundation we need for developing and testing social and economic models. .